Search Results (917)

Cutting CO₂ emissions is crucial to face of climate change, and one of the most tried and true means of post-combustion CO₂ capture is by way of chemical absorption. In this work, the effect of titanium dioxide (TiO₂) nanoparticles in a 25 wt% potassium carbonate (K₂CO₃) solution on solvent regeneration is investigated. This research follows the previous work in which the effect of nanofluids was evaluated on CO₂ absorption. Desorption was studied at three different temperatures (343.15, 348.15 and 353.15 K), using the absorbent fluid with and without 0.06 wt% TiO₂ nanoparticles. The results indicate that the nanofluid enhanced the CO₂ release rates, also reducing energy consumption. The mass transfer was intensified by the presence of nanoparticles, which in turn increased CO₂ diffusivity and influenced the liquid boundary layer, resulting in an enhanced desorption rate, because of the higher diffusivity. These enhancements were achieved with negligible modifications to the fluid properties, i.e., viscosity. In summary, application of TiO₂-enhanced K₂CO₃ solutions is a practical approach to enhance CO₂ removal performance and reduce operating costs such that CO₂ capture is beginning to be environmentally and economically more competitive for the existing system retrofit. Full article

Hydrogen is emerging as a key energy vector for the transition toward renewable and sustainable energy sources. However, its safe and efficient storage remains a significant technical challenge in terms of cost, safety, and performance. In this study, we aimed to address the kinetic limitations of Mg by synthesizing catalyzed Mg@Ni systems using commercially available micrometric magnesium particles (~26 µm), which were decorated via electroless nickel plating under both aqueous and anhydrous conditions. Morphological and compositional characterization was carried out using SEM, EDS, and XRD. The resulting materials were evaluated through Temperature-Programmed Desorption (TPD), DSC, and isothermal hydrogen absorption/desorption kinetics. Reversibility over multiple absorption–desorption cycles was also investigated. The synthesized Mg@NiB system shows a reduction of 37 °C in the hydrogen release activation temperature at atmospheric pressure and a decrease of 167.3 °C under high vacuum conditions (4.5 × 10⁻⁷ MPa), in addition to a reversible hydrogen absorption/desorption capacity of 3.5 ± 0.09 wt.%. Additionally, the apparent activation energy for hydrogen desorption was lower (161.7 ± 21.7 kJ/mol) than that of hydrogenated commercial pure magnesium and was comparable to that of milling MgH₂ systems. This research is expected to contribute to the development of efficient and low-cost processing routes for large-scale Mg catalysis. Full article

This study reports the separation of methyl ethyl ketone (MEK), a relevant compound in the biorefinery context, from aqueous solutions using activated carbons derived from avocado seed biomass. Two synthesis routes were explored via chemical and thermal activation with H₂SO₄ and KOH. A Taguchi experimental design was applied to tailor synthesis conditions, with MEK adsorption capacity as the target property. Adsorption kinetics and isotherms were evaluated to determine the thermodynamic behavior of MEK separation using the best-performing activated carbons. The carbon activated with H₂SO₄ achieved the highest adsorption capacity (142 mg g⁻¹) at 20 °C and pH 4, surpassing KOH-based materials. This enhanced performance correlated to increased surface area and acidic oxygenated functionalities. However, higher pH and temperature reduced the adsorption efficiency for all adsorbents. Comprehensive characterization was performed using XRD, XRF, FTIR, SEM, N₂ adsorption–desorption isotherms, pH at point of zero charge, and surface acidity/basicity analysis via Boehm titration. Thermodynamic data and surface characterization indicated that MEK adsorption occurs via a double-layer mechanism dominated by electrostatic interactions and hydrogen bonding. The findings highlight an optimized approach for tailoring avocado-based activated carbons to efficiently recover MEK from aqueous media, supporting its potential application in downstream purification of fermentation broths for biofuel production and energy transition processes. Full article

Nanofluidic memristors are an emerging class of devices that harness ion transport in confined nanoscale environments to achieve tunable resistance states, mimicking biological synaptic functions. The regulation of ion migration, accumulation, and depletion in nanofluidic channels is fundamentally governed by chemical principles, including surface charge modulation, electrostatic interactions, and ion adsorption and desorption processes. This review provides a comprehensive overview of the chemical foundations of nanofluidic memristors, including electric double layer theory, ion transport dynamics, and interfacial chemistry. Additionally, this review further explores how interfacial chemical modifications, such as functionalization with charged species, pH-responsive coatings, and ionic selectivity molecules, influence nanofluidic memristive behaviors. Representative case studies are discussed to illustrate the practical implementation of these principles in applications ranging from neuromorphic computing to biosensing and energy storage. By bridging fundamental chemical theories with real-world applications, this review aims to provide insights into the rational design of next-generation nanofluidic memristive devices. Full article

Photocatalytic water splitting for hydrogen production is an attractive renewable energy technology, but the oxygen evolution reaction (OER) at the anode is severely constrained by a high overpotential. The two-dimensional vdW ferromagnetic material Fe₃GeTe₂, with its good stability and excellent metallic conductivity, has potential as an electrocatalyst, but its sluggish surface catalytic reactivity limits its large-scale application. In this work, we adapted DFT calculations to introduce surface Te vacancies to boost OER performance of the Fe₃GeTe₂ (001) surface. Te vacancies induce the charge redistribution of active sites, optimizing the adsorption and desorption of oxygen-containing intermediates. Consequently, the overpotential of the rate-determining step in the OER process of Fe₃GeTe₂ is reduced to 0.34 V, bringing the performance close to that of the benchmark IrO₂ catalyst (0.56 V). Notably, the vacancies’ concentration and configuration significantly modify the electronic structure and thus influence OER activity. This study provides important theoretical evidence for defect engineering in OER catalysis and offers new design strategies for developing efficient and stable electrocatalysts for sustainable energy conversion. Full article

Phase change absorbents are deemed a promising alternative for CO₂ capture due to their excellent CO₂ absorption performance, good stability, and low renewable energy consumption. To address the issues of insufficient loading capacity, low regeneration efficiency, and high energy consumption during regeneration in current chemical absorbents, a novel phase change absorbent was developed. As an amino acid ionic liquid phase change absorbent with tetraethylenepentamine as the cation, imidazole as the anion, and n-propanol as the phase separation agent, this absorbent offers a potential solution. The highest absorption capacity of the [TEPAH][Im]/NPA/H₂O system at the optimal n-propanol-H₂O ratio (1:1) reaches 1.34 mol·mol⁻¹, and the viscosity of the CO₂-rich phase amounts to a mere 3.58 mPa·s. Additionally, the desorption efficiency reached 91.1% at 363.15 K, while the loading capacity in the fifth cycle remained over 1.16 mol·mol⁻¹. As n-propanol is present in the [TEPAH][Im]/NPA/H₂O system, the rich phase makes up roughly 30% of the total volume. The energy consumption for regeneration of the [TEPAH][Im]/NPA/H₂O phase change absorption system is 2.20 GJ·t⁻¹ CO₂. Under identical regeneration conditions, the system can reduce the regeneration energy consumption by 41.6%. Full article

To achieve energy conservation, emission reduction, and green low-carbon goals for gas storage facilities, it is crucial to efficiently recover and utilize waste heat during gas injection while maintaining natural gas cooling rates. However, existing sensible and latent heat storage technologies cannot sustain long-term thermal storage or seasonal utilization of waste heat. Thermal chemical energy storage, with its high energy density and low thermal loss during prolonged storage, offers an effective solution for efficient recovery and long-term storage of waste heat in gas storage facilities. This study proposes a novel heat recovery method by combining a moving bed with mixed hydrated salts (CaCl₂·6H₂O and MgSO₄·7H₂O). By constructing both small-scale and full-scale three-dimensional models in Fluent, which couple the desorption and endothermic processes of hydrated salts, the study analyzes the temperature and flow fields within the moving bed during heat exchange, thereby verifying the feasibility of this approach. Furthermore, the effects of key parameters, including the inlet temperatures of hydrated salt particles and natural gas, flow velocity, and mass flow ratio on critical performance indicators such as the outlet temperatures of natural gas and hydrated salts, the overall heat transfer coefficient, the waste heat recovery efficiency, and the mass fraction of hydrated salt desorption are systematically investigated. The results indicate that in the small-scale model (1164 × 312 × 49 mm) the outlet temperatures of natural gas and mixed hydrated salts are 79.8 °C and 49.3 °C, respectively, with a waste heat recovery efficiency of only 33.6%. This low recovery rate is primarily due to the insufficient residence time of high-velocity natural gas (10.5 m·s⁻¹) and hydrated salt particles (2 mm·s⁻¹) in the moving bed, which limits heat exchange efficiency. In contrast, the full-scale moving bed (3000 × 1500 × 90 mm) not only accounts for variations in natural gas inlet temperature during the three-stage compression process but also allows for optimized operational adjustments. These optimizations ensure a natural gas outlet temperature of 41.3 °C, a hydrated salt outlet temperature of 82.5 °C, a significantly improved waste heat recovery efficiency of 94.2%, and a hydrated salt desorption mass fraction of 69.2%. This configuration enhances the safety of the gas injection system while maximizing both natural gas waste heat recovery and the efficient utilization of mixed hydrated salts. These findings provide essential theoretical guidance and data support for the effective recovery and seasonal utilization of waste heat in gas storage reservoirs. Full article

When coal gasification slag is used as a substitute for cement, the prepared cementitious materials may exhibit inadequate properties due to the slag’s limited hydration reactivity, which limits its effectiveness in applications of backfill materials. In this study, alkali activation was used to improve the hydration activity of coal gasification slag. The effect of alkali equivalent on the setting time, rheological properties, and uniaxial compressive strength of the alkali-activated coal gasification slag-based backfill material (ACBM) sample was systematically investigated, and the optimal alkali equivalent was identified. The mineral composition, pore structure, and micromorphology of ACBM samples were characterized using the X-ray diffractometer (XRD), nitrogen adsorption–desorption analyzer (BET), and scanning electron microscope–energy dispersion spectrum (SEM-EDS). The results show that when the alkali equivalent is 4%, the comprehensive performance of ACBM samples is optimal. At this time, the initial setting time and final setting time of ACBM samples are 125 min and 172 min, and the rheological properties are in accordance with the Herschel–Bulkley model. The yield stress, plastic viscosity, and hysteresis loop area are 9.22 Pa, 0.74 Pa·s, and 1014 Pa/s, respectively, and the compressive strength of the ACBM sample at the curing age of 28 days is 2.18 MPa. When the alkali equivalent is further increased to 6%, the initial hydration reaction becomes more intense due to the excessive alkali level, leading to a rapid decline in flowability; the sample cracked at 28 days and its strength decreased considerably. This study provides theoretical guidance for the application of coal gasification slag in the field of backfill mining. Full article

In the thermochemical sulfur–iodine water splitting cycle for hydrogen production, the hydrogen iodide (HI) decomposition reaction serves as the rate-determining step, and its high efficiency relies on the precise design of active sites on the catalyst. This paper combines experimental characterization with density functional theory (DFT) calculations, focusing on activated carbon catalysts. By regulating the types and contents of oxygen-containing functional groups through H₂ reduction treatment at different temperatures, the influence of oxygen-containing functional groups on HI decomposition was investigated. The results show that H₂ reduction treatment can gradually remove oxygen-containing functional groups such as carboxyl, hydroxyl, and carbonyl groups on the surface of activated carbon without significantly affecting the pore structure. Catalytic activity tests conducted under the typical reaction temperature of 500 °C confirmed that as the content of oxygen-containing functional groups decreases, the HI decomposition efficiency increases. DFT calculations further revealed the role of oxygen-containing functional groups: they inhibit the chemisorption of reactant HI on unsaturated carbon atoms and alter the desorption activation energy of product H₂, thereby affecting the overall reaction process. This study provides important theoretical guidance and experimental basis for designing efficient HI decomposition catalysts. Full article

Carbon dioxide (CO₂) is the primary component contributing to anthropogenic greenhouse gas emissions, necessitating the adoption of effective mitigation strategies to promote environmental sustainability. Among the various carbon capture methodologies, chemical absorption is acknowledged as the most scalable solution for post-combustion applications. This investigation presents a thorough, comparative, and scenario-based evaluation of both singular and blended amine solvents for CO₂ capture within packed absorption–desorption columns. A validated rate-based model employing monoethanolamine (MEA) functions as the benchmark for executing process simulations. Three sequential scenarios are meticulously examined to switch the solvents and see the results. In the preliminary scenario, baseline performance is assessed by applying MEA to achieve the designated 73% removal target. Then the implementation of alternative solvents is examined—piperazine (PZ), a combination of methyldiethanolamine (MDEA) and PZ, and a blend of MEA and PZ—under uniform design parameters to ascertain their relative effectiveness and performance. In the second scenario, the design of the system is changed to reach a CO₂ removal efficiency for MEA of 90%, and then MEA is switched to other solvents. In the final scenario, critical design parameters, including column height and diameter, are adjusted for each solvent system that did not meet the 90% capture efficiency in Scenario 2 to achieve 90% CO₂ capture. A comprehensive sensitivity analysis is subsequently conducted on the adjusted systems to evaluate the influence of critical operational variables such as temperature, flue gas and solvent flow rates, and concentrations. Importantly, the MEA + PZ blend also demonstrated the lowest specific reboiler duty, as low as 4.28 MJ/kg CO₂, highlighting its superior energy efficiency compared to other solvents in the condition that the system in this study is pilot-scale, not commercial-scale, and due to this reason, the energy consumption of the system is slightly higher than the reported value for the commercial-scale systems. The results yield invaluable insights into the performance trade-offs between singular and blended amines, thereby facilitating the development of more efficient CO₂ capture systems that function within practical constraints. Full article

The use of organic amine absorbents in CO₂ capture technologies is highly significant. The widespread application of this technique is limited by the heat-stable salts (HSSs) produced during the cyclic absorption–desorption process. This research focused on the HSS removal process using electrodialysis technology and systematically examined the effects of operating voltage, initial concentration, pH, current density, the ratio of liquid volume in the enriched chamber to that in the diluting chamber, and the type of ion-exchange membrane on desalination efficiency, energy consumption, and amine loss. An increase in both voltage and initial concentration significantly enhances the rate of water migration. The rate of ion migration is observed to follow the order of Cl⁻ > ${\mathrm{S}\mathrm{O}}_4^{2-}$> F⁻ in a homogeneous membrane, while in a heterogeneous membrane, the order is ${\mathrm{SO}}_4^{2-}$ > Cl⁻ > F⁻. The optimal operating voltage is 10 V, with a pH level of 8 resulting in the highest ${\mathrm{SO}}_4^{2-}$ removal efficiency. An industrial scenario validated the optimized process conditions, which balanced energy consumption with desalination efficiency. This methodology is essential not only for providing a viable solution for the industrial purification of organic amines but also for promoting the environmentally sustainable development of carbon capture technologies. Full article

This paper discusses the integrated technology of CO₂ adsorption and catalysis, which combines adsorption and catalytic conversion, simplifies the traditional process, reduces energy consumption, and improves efficiency. The traditional carbon capture technology has the problems of high energy consumption, equipment corrosion, and absorbent loss, while the integrated technology realizes the adsorption, conversion, and catalyst regeneration of CO₂ in a single reaction system, avoiding complex desorption steps. Through micropore confinement and surface electron transfer mechanism, the technology improves the reactant concentration and mass transfer efficiency, reduces the activation energy, and realizes the low-temperature and high-efficiency conversion of CO₂. In terms of materials, MOF-based composites, alkali metal modified oxides, and carbon-based hybrid materials show excellent performance, helping to efficiently adsorb and transform CO₂. However, the design and engineering of reactors still face challenges, such as the development of new moving bed reactors. This technology provides a new idea for CO₂ capture and resource utilization and has important environmental significance and broad application prospects. Full article

Although concentrated solar power (CSP) coupled with calcium looping (CaL) offers a promising avenue for efficient thermal chemical energy storage, calcium-based sorbents suffer from accelerated structural degradation and decreased CO₂ capture capacity during multiple cycles. This study used Density Functional Theory (DFT) calculations to investigate the mechanism by which Mg and Ni doping improves the adsorption/desorption performance of CaO. The DFT results indicate that Mg and Ni doping can effectively reduce the formation energy of oxygen vacancies on the CaO surface. Mg–Ni co-doping exhibits a significant synergistic effect, with the formation energy of oxygen vacancies reduced to 5.072 eV. Meanwhile, the O²⁻ diffusion energy barrier in the co-doped system was reduced to 2.692 eV, significantly improving the ion transport efficiency. In terms of CO₂ adsorption, Mg and Ni co-doping enhances the interaction between surface O atoms and CO₂, increasing the adsorption energy to −1.703 eV and forming a more stable CO₃²⁻ structure. For the desorption process, Mg and Ni co-doping restructured the CaCO₃ surface structure, reducing the CO₂ desorption energy barrier to 3.922 eV and significantly promoting carbonate decomposition. This work reveals, at the molecular level, how Mg and Ni doping optimizes adsorption–desorption in calcium-based materials, providing theoretical guidance for designing high-performance sorbents. Full article

Developing and utilizing capture and storage technologies for CO₂ has become a critical research topic due to the significant greenhouse effect caused by excessive CO₂ emissions. A conventional physical absorption process for CO₂ capture is polyethylene glycol dimethyl ether (NHD); however, its limited application range is caused by its poor absorption of CO₂ at low pressures. In this work, the CO₂ absorption of NHD was enhanced by combining NHD with a novel chemical absorbent 2-methylimidazole (2-mIm)-ethylene glycol (EG) solution to improve CO₂ absorption. Viscosity and CO₂ solubility were examined in various compositions. The CO₂ solubility in the mixed solution was found to be at maximum when the mass fractions of NHD, 2-mIm, and EG were 20%, 40%, and 40%, respectively. In comparison to pure NHD, the solubility of CO₂ in this mixed solution at 30 °C and 0.5 MPa increased by 161.2%, and the desorption heat was less than 30 kJ/mol. The complex solution exhibits high selectivity and favorable regeneration performance in the short term. However, it is more sensitive to moisture content. The results of this study can provide important data to support the construction of new low-energy solvent systems and the development of novel CO₂ capture processes. Full article

Direct air capture (DAC), as a complementary strategy to carbon capture and storage (CCS), offers a scalable and sustainable pathway to remove CO₂ directly from the ambient air. This study presents a detailed evaluation of the amine-functionalised metal-organic framework (MOF) sorbent, mmen-Mg₂(dobpdc), for DAC using a temperature–vacuum swing adsorption (TVSA) process. While this sorbent has demonstrated promising performance in point-source CO₂ capture, this is the first dynamic simulation-based study to rigorously assess its effectiveness for low-concentration atmospheric CO₂ removal. A transient one-dimensional TVSA model was developed in Aspen Adsorption and validated against experimental breakthrough data to ensure accuracy in capturing both the sharp and gradual adsorption kinetics. To enhance process efficiency and sustainability, this work provides a comprehensive parametric analysis of key operational factors, including air flow rate, temperature, adsorption/desorption durations, vacuum pressure, and heat exchanger temperature, on process performance, including CO₂ purity, recovery, productivity, and specific energy consumption. Under optimal conditions for this sorbent (vacuum pressure lower than 0.15 bar and feed temperature below 15 °C), the TVSA process achieved ~98% CO₂ purity, recovery over 70%, and specific energy consumption of about 3.5 MJ/KgCO₂. These findings demonstrate that mmen-Mg₂(dobpdc) can achieve performance comparable to benchmark DAC sorbents in terms of CO₂ purity and recovery, underscoring its potential for scalable DAC applications. This work advances the development of energy-efficient carbon removal technologies and highlights the value of step-shape isotherm adsorbents in supporting global carbon-neutrality goals. Full article